help with compression ratio

[stewartfn18]

after searching and not finding what i want, and not knowing how to use the cr calc, i need some help. my current setup is bens old stage 2 cam, 3500 heads, and stock rotating assembly. i know my compression is like 9.1:1 and im looking to bump that up. ive looked at both the iron head piston swap and lq1 piston swap. i know that the cr with the 3500 heads and iron head pistons is going to be ~11.5:1. what about the Dohc pistons. also, should i use 3400 gaskets to keep the .060 compressed thickness, or something else.

[bszopi]

Maybe this will help...? http://60degreev6.com/content.php/20...-CR-Calculator

[stewartfn18]

let me rephrashe. i know how to use the cr clac, but i dont know the values of the combustion chamber size, piston dome, which doesnt make sense because they are valve relief pistons, and what ever the last value is, i cant find those.

[bszopi]

Ok. I'm at work and can't work through the numbers right now, but I will try to do it for you later. And I'll try to explain where I got the numbers from as well.

Sent from my DROID2 GLOBAL using Tapatalk

[bszopi]

Ok, here we go...

First, we have your current setup:


Next is iron head pistons and aluminum head gaskets:


Next is iron head pistons and iron head gaskets:


Next is DOHC pistons and aluminum head gaskets:


And finally, DOHC pistons and iron head gaskets:


All this info is available in the CR calc. That's why I pointed you to the article, as it explains how to get values from other engines, as well as gives an explanation of what each of the inputs is. All you need to do is load up whatever engine you want to use parts from (the 3.4 iron head, 3.4 DOHC, and 3500 in this case), and write down their values for the parts you want to use. Then, load up your engine (3400 in your case) and select User Entered Values, then type in the various numbers for the combo you are looking for.

[stewartfn18]

thanks man, thats what i was looking for. i just couldnt find the values of the parts that i had/wanted. thanks again, thats a ton of help. one more question, i know trying to tune 12.5:1 on pump gas is tricky, would 12.2 be able to be done with 12.2 or is it still gonna be a pain? 11.5 is really what i was shooting for but i found a hell of a deal on dohc pistons.